UPSC Prelims 2015— Question 95

Correct answer: Option A. A hydrogen fuel cell converts chemical energy into electrical energy through an electrochemical reaction. With pure hydrogen and oxygen, the main products are electricity, heat and water. Fuel cells can be used in large stationary systems as well as portable applications. The electricity generated is direct current at the cell level and requires power electronics for AC applications. Thus only statement 1 is correct. Option-wise analysis: Option A: “1 only” is correct. It directly matches the factual or conceptual requirement tested by the question and is supported by the principle explained above. Option B: “2 and 3 only” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Option C: “1 and 3 only” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Option D: “1, 2 and 3” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Prelims takeaway: Focus on the precise institutional role, constitutional provision, geographical association, or technical definition being tested. UPSC questions often place a broadly familiar fact beside a narrowly incorrect qualifier; identifying that qualifier is essential for elimination.